The control of oil and/or gas production wells has become increasingly complex. Wells under the control of a single company are being drilled throughout the world. Therefore, the need for central control of wells that are widely dispersed geographically presents challenges to the communication of sensor and logging information from the wells to the central controller and to the communication of control information from the central controller to the wells.
Moreover, the wells themselves have become increasingly more complex. For example, well holes are being drilled with multiple branches and are being divided into multiple production zones that discretely produce fluid in either common or discrete production tubing. As a result, the importance of communications between zones of a well, between the well and the surface, and between wells has increased.
As a consequence, it is known to position sophisticated computer and telecommunication equipment at the surface of wells and within the wells for supporting the communication of sensor, logging, and control information. The equipment within the well hole has usually been hardwired together and to the equipment at the surface. However, signals have also been acoustically communicated between this equipment. In this latter case, the information and control signals may be acoustically communicated at variable frequencies, at specific fixed frequencies, and/or using codes. Also, such acoustic signals may be transmitted through casing streams, electrical lines, slick lines, subterranean soil, tubing fluid, and/or annulus fluid.
Transmitters that convert electrical signals to acoustic signals are used to transmit the acoustic signals, and receivers that convert the acoustic signals back to electrical signals are used to receive the acoustic signals. These transmitters and receivers typically include transducers, such as piezoelectric transducers, to perform the required conversions. Piezoelectric transducers generate a mechanical force when alternating current voltage is applied thereto. The signal generated by the stressing of the piezoelectric transducers travels along the borehole between transmitters and receivers that are situated at the various sensing and control locations along the well and at the surface.
When acoustic signals are used to communicate sensor, logging, and control information through a well, various acoustic signal impairments, such as echoes, flow and machine noise, and reverberations, can interfere with the accurate recovery of the sensor, logging, control information from the acoustic signals. The present invention addresses this problem by coating the transducers of a down hole communication system with an anechoic material.